Please ask whoever is trying to remove the numbers to make sure they read all the instructions, assemble all the supplies in advance, test carefully, watch for possible problems as they proceed and be ready to stop and ask for more help if things seem strange or worrying. This is the way we would remove the numbers in Britain, but you should make sure that the method and materials are appropriate for your situation.
A clear, safe area to work, with some acid-free tissue or absorbant white paper towelling on the work surface. If the table or bench surface is not solvent proof, put a sheet of polythene on the tabletop under the tissue. A pencil, notebook and camera. The correct materials to reapply the number or at least safe tie-on labels and a fade-proof, waterproof pen to write the number on the labels. Cotton wool and toothpicks or bamboo kebab sticks (you can use commercial cotton wool buds but they are not as good as ones you make yourself). A solvent-proof container to put the used cotton wool in (a small glass jar with a screw top metal lid is fine). A small amount of acetone in a safe container (another glass jar with a metal screw top lid will work as a temporary container for the small amount you should have in your work area – please make sure it is labelled ACETONE and FLAMMABLE). Acetone fumes are very flammable so have good ventilation in the area and make sure there are no hot surfaces or naked flames nearby. It is a good idea to have the acetone and waste jars in a small polythene or metal tray in case anything gets knocked over. Make sure you can see clearly what you are doing and that both you and the objects will be safe in the area. You may need pads of tissue or polythene foam to rest the pot on to make sure it cannot roll or fall over. A pair of impermeable gloves such as nitrile or polythene that fit well. Make sure you tie long hair back and are not wearing anything that could catch on the object or the kit you are working with (e.g. spectacles dangling on a cord, an open jacket or cardigan, a necklace or large bracelet or ring).
1. Make a careful note of the number and preferably take some clear photos of it and the pot so there is no danger of losing or confusing the numbers.
2.Place the pot in a position so it is safe and you can clearly see the area where you will be working.
3. Take a small piece of cotton wool and roll it around the tip of the toothpick or bamboo kebab stick. The easiest way to do this it to place the small amount of cotton wool on the tip of your forefinger, rest the tip of the stick on the cotton wool, close your thumb over the cotton and stick. Hold the other end of the stick in between the thumb and forefinger of your other hand and rotate it to wind the cotton wool around it. Practise until you are comfortable with this. You can pull unsuccessful cotton wool swabs off the stick, tease them apart and reuse them (or throw them in the waste jar).
4. When you have successfully made a small cotton wool swab, dip the tip of it in your small jar of acetone so it is only immersed halfway. You don’t want it to be dripping solvent, so if you have too much on the cotton wool, press the swab against the inside rim of the jar and let the excess acetone run back down inside the jar. Apply the tip of the swab to a small area of the pot near the number, but in a discreet area. Gently roll it to and fro a few times. Look at the tip of the swab. Has any colour come off the pot? Look at the pot – does the surface seem softened or changed in any way ? It will look dark at first until the acetone evaporates, but if it looks different after that you may have a surface which is affected by solvents and you should show the pot to a conservator before proceeding. Common examples of such problems are – the pot is not really ceramic or it has a painted decoration, a gapfill or a repair which dissolves in acetone. Pull the dirty swab off the stick and put it in your waste jar.
5. If nothing unexpected happens and the pot seems unchanged after the solvent has evaporated from the test area, take a fresh swab of acetone and, ALWAYS working from the edge in to the middle of the numbered area, gently roll the swab to and fro on a small area of the painted number. You will need to change the swab often and be careful not to allow excess acetone to flow across the surface of the pot or you may spread the White-out, the Sharpie ink or the nail varnish and smear it into the body of the ceramic. Always work towards the centre, clean one area and then move on to the next. Never roll a dirty swab across the object, always remove it and replace with a clean one.
6. When you have finished, make a note of what you have done. This is part of the history of the object and should be recorded. Include any observations you made about the pot while you worked on it. You may have noticed something that no-one else has.
7. Dispose of the used swabs carefully and return unused acetone to a safe store. Do not return the acetone in the jar to the main container as it may have a small amount of contaminants such as cotton wool fibres (fibers).
8. Apply the number using the correct materials. These are listed in the helpful guidelines on Collections Link at http://www.collectionslink.org.uk/programmes/spectrum/682-labelling-and-marking-museum-objects-spectrum-40
Paraloid used to be known in the USA as Acryloid.
I hope this helps.